The present invention relates to an article of furniture, particularly a chair, comprising a tiltable seat associated with a reclining back rest, which includes an adjusting device including a stored power source for restoring the seat and back rest from a reclining to a normal position, and in which the several elements are so arranged that the change in inclination of the seat and back rest are synchronously coupled to one another. The term "chair", as used hereinafter, is intended to encompass all such articles of furniture.
Various designs of chairs having adjusting devices for synchronously coupling the seat and back rest are already known in the art. These designs usually include one or more stored power elements which hold the back rest and seat at a fixed starting position under no load conditions, and which restore the back rest and seat to this starting position after an applied force, e.g. due to movement of the upper body of a user, is removed. Compression, tension, and so-called "fluid" springs have been used as such stored power elements and, in the known arrangements, are usually placed horizontally under the seat of the chair.
One disadvantage of the above arrangement is that, due to unfavorable leverage ratios, the back rest tends to follow the movement of the upper body of the user in a faltering manner when a person sitting on the chair moves forwardly to relieve the force being applied to the back rest. This results from the fact that the weight of the user's body continues to apply a load to the seat, which is synchronously coupled to the back rest, during such movement. In some prior designs, it is even necessary for the user to rise from the seat in order to allow the seat and back rest to be brought forward by the stored power element. In contrast, one object of the present invention is to provide a chair, of the type having synchronously coupled seat and back rest portions, wherein the back rest follows more smoothly the movements of the upper body of the user, and wherein the back rest and seat can return without delay to their original no-load positions.
Other designs of chairs have been suggested which provide the smoother flow of motion achieved by the present invention, and achieve this result by a more favorable selection of leverage ratios. However in these other designs, the stored power elements must be arranged parallel to the upright part of the chair, and open to view, or at such a great distance below the seat that the stored power elements are always visible in an annoying and unattractive manner. In contrast, another object of this invention is to provide a chair which exhibits such more favorable leverage ratios but wherein the stored power element is not open to view, resulting in a more esthetically pleasing design.